To answer your question regarding motivation, I'd say there isn't a definite way of getting motivated. Different people get motivated by different things. The fact is, motivation doesn't get you to your goal. Grounded efforts and habits do. Just like you brush your teeth everyday, while no one tells you to do so. You don't look for motivation for that or to take a shower. That's because they have become a part of your daily routine, they have turned into habits. Likewise, you need to transform the workout task into a habit. After that, you wouldn't look for motivation. I'm not saying there's something wrong in being motivated by something, but in most cases, motivation is temporary. Habits are permanent and they die hard. Do it till the point you feel like doing it.
Regarding feeling exhausted and fatigued, there may be several reasons for that. First thing is your diet. You need to eat enough in order to sustain energy all day long and to get fully nourished. Keep drinking water regularly, to keep yourself hydrated. This is very important as we are made up of 70% water. You also need to get adequate sleep. When you sleep, your muscles undergo the repair work, so it's very important to have a good sleeping pattern.
I'm no expert on protein drinks and energy drinks, so I can't advise on those. Now taking your workout pattern into consideration, 5 sets of bench press? The things to be considered are the rep/set, the weight you lift per set. Also, if you are doing it right with correct form, or just getting it done.
If you ask me, 5 sets of press with an average of 10 reps for set, gives you 50 reps. That's good enough for a day. I usually lift heavy, so I never go beyond 3 sets of any exercise.